Question

you have a piggy bank containing 78 coins in dimes and quarters. If the piggy bank contains $12.60, how many dimes in the piggy bank?

Answer 1

so if q = quarters and d = dimes

Answer 2

q+d=78

Answer 3

.25q+.10d=$12.60

Answer 4

that's perfect, now just solve the system

Answer 5

ok so i would multiply 4 through out equation 2 right?

Answer 6

personally, I would use substitution instead

Answer 7

like .25q=$12.60-10d?

Answer 8

q+d=78
q= 78-d

0.25q+0.10d=$12.60
0.25(78-d) + 0.10d = 12.60

Answer 9

the first equation is much easier to solve for one variable, then sub into the other.

Answer 10

19.5-0.25d+0.10d=12.60 turns into 19.5+.15d=12.60 and then .15d=6.9?

Answer 11

so how many dimes were in the bank?
then we know from before that q= 78-d

Answer 12

46 dime and 15 q?

Answer 13

your quarters is wrong, use q= 78-d

Answer 14

oh thought it was suppose to be 61 coins my mistake but then q=32?

Answer 15

right, good job.

Answer 16

wow thanks the way teacher taught me was confusing is substitution easier in these situations?

Answer 17

when you are dealing with decimals, and small number, substitution is generally easier as you cannot always find a convenient multiple